Apparatus for compensation of right and left pincushion distortion

ABSTRACT

Apparatus for compensation of right and left pincushion distortion comprising a closed magnetic circuit having a saturable magnetic core with right and left half portions symmetrical to one another and a branched portion defining an air gap and symmetrically arranged with respect to the right and left half portions. The branched portion can be centrally located in the core or can be disposed at opposite ends thereof. A pair of first and second windings are wound on each of the right and left half portions, the first windings of both pairs being connected in series so as to have the same winding directions in relation to the saturable magnetic core and being adopted for being connected to a vertical deflection circuit, whereas the second windings of both pairs are connected in series so as to have reverse winding directions in relation to the saturable magnetic core and are adapted for being connected to a horizontal deflection circuit.

Waited States Patent Horie et a1.

[ Dec. 10, 1974 1 APPARATUS FOR COMPENSATION OF RIGHT AND LEFTPINCUSHION DISTORTION Inventors: Einosuke Horie; Masakazu Kikuchi,

both of Takasaki; Shigekazu Hatori, Gunma, all of Japan [21] Appl. No.:435,588

Primary Examiner-G. Harris Attorney, Agent, or Firm-Waters, Roditi,Schwartz & Nissen [57] ABSTRACT Apparatus for compensation of right andleft pincushion distortion comprising a closed magnetic circuit having asaturable magnetic core with right and left half portions symmetrical toone another and a branched portion defining an air gap and symmetricallyarranged with respect to the right and left half portions. The branchedportion can be centrally lo- [30] Forelgn Apphcauon Pnomy Data cated inthe core or can be disposed at opposite ends Jan. 23, 1973 Japan 48-9201th fi A pair of first and second windings are wound 1, 1973 Japan48-24670 on each of the right and left half portions, the first windingsof both pairs being connected in series so as [52] US. Cl. 335/210,315/27 SR to have the ame winding directions in relation to the [51]Int. Cl. 01f 7/00 saturable magnetic core and being adopted for being[58] Field of Search 335/2 connected to a vertical deflection circuit,whereas the 315/27 SR second windings of both pairs are connected inseries so as to have reverse winding directions in relation toReferences Cited the saturable magnetic core and are adapted for beingUNITED STATES PATENTS connected to a horizontal deflection circuit.

3,325,675 6 1967 Sanford 313/75 X 3,781,590 12i1973 Chapman... 315/27 SR6 Clams l0 Drawmg guns 9 101i) 101 q 2 102 1 l i [i P l l 101a i 4 i N24,0 1071) 104B -107 10s \4 109a 09 7- I08 105a 103 r, i a

gi/05b g 702 PATENTEL LEE I 0 I974 SHEET 10F 3 4 PRIOR ART I I?! ARPRIOR ART Pmiwzunm 3,854,108

SHEEPMF 3 APPARATUS FOR COMPENSATION OF RIGHT AND LEFT PINCUSI-IIONDISTORTION BACKGROUND This invention relates to apparatus for thecompensation of right and left pincushion distortion in a colortelevision set.

In general, the raster in a color television set becomes larger in rightand left pincushion distortion as the deflection angle of a Braun tubeis increased. Conventionally, to compensate for these distortions, thetransformer including an E I type saturable magnetic core has been usedin such a manner that a horizontal deflection current isamplitude-modulated into a parabolic wave form so that the horizontaldeflection current is maximum in amplitude at the middle of eachvertical scanning period. Namely, as shown in FIG. 1, an E type magneticcore 1 and an I type magnetic core 2 are joined together to form acomposite magnetic core of E I type, whose center leg portion 3 thereofis provided with a winding or coil 4, and whose opposite side legportions 5a, 5b are provided with respective windings or coils 6a, 6b,the coils 6a, 6b being connected in series at a point 7.

The operation of the resultant transformer is as follows:

Opposite terminals 8a, 8b of the series connected coils 6a, 6b areconnected in series to a horizontal deflection coil (not illustrated) inan image receiving set and when a horizontal deflection current flowsthrough the coils 6a, 6b, magnetic fluxes arising from the deflectioncurrent are generated as shown by the solidline arrows 9a, 9b, and thesefluxes 9a, 9b are reversed in direction at the center leg portion 3' andhence oppose one another so that a net voltage (horizontal deflectionvoltage) based on these fluxes is not induced in the coil 4. As, in thiscase, an electric current of a parabolic wave form having a verticaldeflection frequency is passed, while superposed on a direct electriccurrent, between the terminals of the coil 4, this current producesfluxes 10a, 10b as shown in dotted lines which serves as a controlcurrent for changing the degree of magnetic saturation at the center legportion 3' and at the opposite side leg portions 5a, 5b. As a resultthereof, the inductance of the coils 6a, 6b viewed from the terminals8a, 8b is modulated and thereby the electric current flowing through thehorizontal deflection coil is amplitude-modulated into a parabolic waveform with the frequency of vertical deflection.

When, in this case, the relation between the inductance presented in thecoils 6a, 6b and the control electric current is examined with thehorizontal deflection current varied as a parameter, the relation is asshown in FIG. 2. Namely, a curve A is obtained when the horizontaldeflection current is zero, a curve D when the current is of maximumvalue, and curves B, C when the current is of intermediate values. Itcan be seen from FIG. 2 that the inductance of the coils is modulatedaccording to the parabolic wave forms of the control current in thecases of the curves A, B, and C but the inductance is substantiallyunmodulated in the case of the curve D. It is assumed that this isascribable to the fact that the magnetic core at the opposite side legportions approaches its saturated condition under the influence of thehorizontal deflection current. When, accordingly, a vertical directionraster on the Braun tube is viewed, a complete compensation of thepincushion distortions in the vicinity of right and left end portions isdifficult. Since it is usual that a distortion compensation apparatus isso designed that it uses a case where the foregoing inductance changecharacteristic feature is linear as in the case of the curve B of FIG.2, the horizontal deflection current is small in the vicinity of theraster center portion and an inductance change along the cruve A isbrought about, and as a result the distortion compensation becomesexcessive and a distortion in the reverse direction is brought about atthat portion. Thus, the result is that the raster, in the case of use ofthe conventional distortion compensation apparatus, is such thatdistortions remain as shown in FIG. 3.

SUMMARY OF THE INVENTION An object of the present invention is toprovide pincushion distortion compensation apparatus to overcome theforegoing deficiencies and in which apparatus the magnetic core isprevented from being saturated with the electric current of thehorizontal deflection current coils while completely compensating rightand left pincushion distortions.

For achieving this object, it can be first considered, that thehorizontal deflection current coils 6a, 6b are connected so as to bereverse in winding directions. In this case, however, the magneticfluxes 9a, 9b in FIG. 1 have the same directions at the center legportion 3 and are additive thereat whereby a saturation phenomenon israpidly produced at that portion so that the control current does notoperate effectively. It can be also considered that the center legportion 3' of the magnetic core is entirely removed and the coil 4provided near the coils 6a, 6!) on the opposite side leg portions. Inthis case, however, the magnetic fluxes 9a, 9b of the coils 6a, 6bentirely negate one another and the coils 6a, 6b become useless. Theinvention is predicated on the concept that it can be considered that,concerning the center leg portion 3 of the conventional apparatuswherein the winding directions of the coils 6a, 6b are reversed, adesirable condition could be obtained between the exsistence and thenonexsistence of the same.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation view of aconventional apparatus for compensation of pincushion distortion,

FIGS. 2 and 3 are diagrammatic illustrations showing characteristicfeatures thereof,

FIG. 4 is a side elevation view of one embodiment of apparatus forcompensation of pincushion distortion according to the invention,

FIG. 5 is a graphical diagram showing a characteristic feature of thesame,

FIG. 6 is a graphical diagram showing a comparison betweencharacteristic features of the conventional apparatus and that of theinvention,

FIG. 7 is a side elevation view of a modified embodiment according tothe invention,

FIG. 8 is a top plan view thereof,

FIG. 9 is a side sectional view, taken along the line IX-IX in FIG. 10,of another modified embodiment according to the invention, and

FIG. 10 is a top plan view thereof.

DETAILED DESCRIPTION Referring to FIG. 4 which shows one embodiment ofthis invention, numeral 1 denotes a saturable magnetic core of a closedmagnetic circuit comprising a circular ring composed of right and leftsemi-circular portions la, lb symmetrical in form with respect to oneanother and numeral 2 denotes a diverged or branched magnetic coreextending in the middle portion of the magnetic core 1 to define an airgap 3 between the magnetic core 1 and the deverged core 2 so as toincrease the magnetic resistance of the diverged magnetic core 2. Theright and left half portions 1a, lb are provided, respectively, with apair of first windings or coils 4a, 4b and a pair of second windings orcoils 5a, 5b wound thereon. The first windings 4a, 4b are connected inseries at a point 6 so as to be the same in winding direc-' tions inrelation to the saturable magnetic core 1, and numerals 7a, 7b denotethe opposite terminals thereof. The second windings 5a, 5b are connectedin series at a point 8 so as to be reverse in their winding directions,and numerals 9a, 9b denote the opposite terminals thereof. The terminals7a, 7b are connected to a vertical deflection circuit (not shown), andthe terminals 9a, 9b are connected to a horizontal deflection circuit(not shown).

With this arrangement, the magnetic fluxes induced in the coils 4a, 4bby the horizontal deflection current flowing through the coils 5a, 5bare made to be reverse in direction, so that no horizontal deflectionvoltage component is generated in the coils 4a, 4b.. When the verticaldeflection current is small in value, the magnetic fluxes generated fromthe coils 4a, 4b are small and the magnetic core 1 is never magneticallysaturated. However, in the condition when the vertical deflectioncurrent is increased and before the magnetic core 1 is saturated, theinductance of the coils 5a, 5b can be modulated as in the conventionalapparatus. The magnetic flux passing through the center leg portion 2 bythe electric current flowing through the coils 5a, 5b does not saturatethe center leg portion 2, because the magnetic resistance is large dueto the presence of air gap 3. When the relation between the inductanceof the coils 5a, 5b and the vertical deflection current value isexamined in substantially the same manner as in the conventional case,the result is as shown in FIG. 5. Therein, curves A D refer tohorizontal deflection current values ofa magnitude corresponding tothose in the case of FIG. 2. It can be noted from FIG. 5, however, thatwhen the horizontal deflection current changes in value, there occursonly a slight difference in the modulation condition of the coil.inductance so that the modulation by the control current is alwayseffected properly. As regards the raster generated according to thisinvention, it is compared with a regular lattice pattern and adistortion thereof is obtained in percent as shown in FIG. 6. In thisFIGURE, curve E is obtained by use of the conventional apparatus, andcurve F is obtained by the embodiment of this invention. It can beappreciated from FIG. 6 that a distortion of about 5 percent is causedat the extreme end portions in the conventional case but it becomes 1.5percent at most according to the invention. Thus, there is obtained anextremely good distortion compensation apparatus, according to thisinvention, while additionally, there is no special difficulty in themanufacturing process and the operation is stable over long periods oftime.

FIGS. 7 and 8 show a modified embodiment of this invention. Therein, asaturable magnetic core 101 of closed magnetic circuit type comprisesright and left half portions 101a, 10lb which are provided at theirright and left outside portions with respective branched or divergedmagnetic cores 102 having respective air gaps 103. In this embodiment,the composite magnetic core is composed of a pair of right and left handdrum type cores G, each having upper and lower circular flanges g withconnecting stems, the cores being suitably cut at their flanges to formflat faces at which they are joined together to form the compositemagnetic core with the saturable magnetic core 101 and the right andleft symmetrical diverged magnetic cores 102, having the air gaps 103.In other respects, this embodiment is not significantly different fromthe previously described embodiment.

FIGS. 9 and 10 show another embodiment of the invention in which thesaturable magnetic core 201 with right and left portions 201a, 201b isprovided at its right and left outside portions with respective branchor diverged magnetic cores 202 having respective air gaps 203. This issubstantially the same as the foregoing embodiments except that thecomposite magnetic core is constituted by a pair of upper and lower pottype cores H, joined together through a pair of right and left stems hWhat is claimed is:

1. Apparatus for compensation of right and left pincushion distortionscomprising a closed magnetic circuit including a saturable magnetic corehaving right and left half portions symmetrical to one another and abranch portion defining an air gap and symmetrically arranged withrespect to said right and left half portions, a pair of first and secondwindings on each of the right and left half portions, the first windingsof both pairs being connected in series so as to have the same windingdirections in relation to the saturable magnetic core and being adaptedfor being connected to a vertical deflection circuit, the secondwindings of both pairs being connected in series so as to have reversewinding directions in relation to the saturable magnetic core and beingadapted for being connected to a horizontal deflection circuit.

2. Apparatus as claimed in claim 1 wherein said branched portion iscentrally disposed with respect to said right and left half portions.

3. Apparatus as claimed in claim 1 wherein said right and left halfportions have opposite outside ends, said branched portion comprising arespective branch section at each of said outside ends of said halfportions.

4. Apparatus as claimed in claim 1 wherein said saturable magnetic coreis in the form of a circular ring, said branched portion extending alonga diameter thereof.

5. Apparatus as claimed in claim 1 wherein said magnetic core isconstituted by a pair of right and left hand drum elements, each havinga pair of upper and lower circular flanges and a connecting stern, eachof the flanges of the drum elements being partly cut to form flat facesat which the drum elements are joined together.

6. Apparatus as claimed in claim 1 wherein said magnetic core isconstituted by a pair of upper and lower pot type core elements withrespective stems, said core elements being joined together through apair of right and left stems.

1. Apparatus for compensation of right and left pincushion distortions comprising a closed magnetic circuit including a saturable magnetic core having right and left half portions symmetrical to one another and a branch portion defining an air gap and symmetrically arranged with respect to said right and left half portions, a pair of first and second windings on each of the right and left half portions, the first windings of both pairs being connected in series so as to have the same winding directions in relation to the saturable magnetic core and being adapted for being connected to a vertical deflection circuit, the second windings of both pairs being connected in series so as to have reverse winding directions in relation to the saturable magnetic core and being adapted for being connected to a horizontal deflection circuit.
 2. Apparatus as claimed in claim 1 wherein said branched portion is centrally disposed with respect to said right and left half portions.
 3. Apparatus as claimed in claim 1 wherein said right and left half portions have opposite outside ends, said branched portion comprising a respective branch section at each of said outside ends of said half portions.
 4. Apparatus as claimed in claim 1 wherein said saturable magnetic core is in the form of a circular ring, said branched portion extending along a diameter thereof.
 5. Apparatus as claimed in claim 1 wherein said magnetic core is constituted by a pair of right and left hand drum elements, each having a pair of upper and lower circular flanges and a connecting stem, each of the flanges of the drum elements being partly cut to form flat faces at which the drum elements are joined together.
 6. Apparatus as claimed in claim 1 wherein said magnetic core is constituted by a pair of upper and lower pot type core elements with respective stems, said core elements being joined together through a pair of right and left stems. 